Fair Value Measurements - Fair Value Inputs of Long-Lived Assets Held and Used (Details)
9 Months Ended 12 Months Ended
Sep. 30, 2016
ft²
$ / ft²
Dec. 31, 2015
ft²
$ / ft²
Retail    
Impaired Long-Lived Assets Held and Used [Line Items]    
Property square footage | ft² 91,817 153,008
Retail | Minimum    
Impaired Long-Lived Assets Held and Used [Line Items]    
Sales price (in usd per sqft) 62.84 41.21
Retail | Maximum    
Impaired Long-Lived Assets Held and Used [Line Items]    
Sales price (in usd per sqft) 214.29 168.30
Retail | Weighted Average    
Impaired Long-Lived Assets Held and Used [Line Items]    
Sales price (in usd per sqft) 110.54 79.90
Industrial    
Impaired Long-Lived Assets Held and Used [Line Items]    
Property square footage | ft² 160,477 375,076
Industrial | Minimum    
Impaired Long-Lived Assets Held and Used [Line Items]    
Sales price (in usd per sqft) 2.50 17.77
Industrial | Maximum    
Impaired Long-Lived Assets Held and Used [Line Items]    
Sales price (in usd per sqft) 38.15 22.00
Industrial | Weighted Average    
Impaired Long-Lived Assets Held and Used [Line Items]    
Sales price (in usd per sqft) 21.59 19.40
Office    
Impaired Long-Lived Assets Held and Used [Line Items]    
Property square footage | ft²   204,936
Office | Minimum    
Impaired Long-Lived Assets Held and Used [Line Items]    
Sales price (in usd per sqft)   58.17
Office | Maximum    
Impaired Long-Lived Assets Held and Used [Line Items]    
Sales price (in usd per sqft)   133.61
Office | Weighted Average    
Impaired Long-Lived Assets Held and Used [Line Items]    
Sales price (in usd per sqft)   104.53